Preparation of sols



Patented Dec. 30, 1947 UNITED r'S' T-AT-E S rimrAmrromon-sots t Mori-is -D. Marshall Arlington,,. Mass.,s assignmmtowMonsanto, Chemicalelcompany, .St. Louis,

1.110., a corporationiof Delaware I WNW-Drawing. -:riginal application SeptemberlB,

This invention .relatest-tow the preparation of sols, and: part cu rlyo the preparati loisubstantially -anhydrous and salt free, qrganosols, such assols containi ng ,certain alcohols, others, v ether-alcohols).esters,ketoneshydmcanbonsand 5 complete removal of the water by distillation, the; like ,as -,the continuous hase.

1 'Lh ea e severa k o n: m thods 01m making ia r nh drous,soreanosols. For example,: ityis qld to a, V ,aQid, tand -then o .emovefltheflwater. by such j iucrganosolswhich arensubstantially" freeof an as'd a s st ri exnosurein aiconfin d space to the d i lacti flp tdry carbonate oipotaSh dd alcoholi adueoussilicic or quicklime. .,It is alsorold, to Midglycer ne; 110.. a

.2% c,o11oidal-,s licic acid=solutioniwithsheatand H a ita o and-th m tt zl vaporatewthe water. t 15 t asecondbr ithrdi' disti lati n; whichmay. r obtaina clear; transna.1t 11 v hi hly v co ma t colioidal s l c c ac dli i s ycerina. 1. Howeve the p ducts prepared. ntheabovemannerare either :of i c nc ntration or oliilowtstab ity.andth r ,fore are nottsuitabletior nanyhindustrial pur-,,,20 {to replace it may befeither. vwater-miscible ".01 "poses: for which-they nu ht therwise be adap It is, accordinglyfa primaryobject of thisi intvention :to prepare-Jem stable and highly .dis-

persed inorganic oxide sols in substantially in Ahflurtherr objectiofithe invention is to prepare substantially 5 anhydrousr sols of. a relatively high ,degree of concentratiomand stability containing teither; aromatic ortaliphatic hydrocarbons as the ling imediumfor continuous 'phase. A-most suit- ;continuous phase.

,,- A still further object of. the invention; is topre- "pare sols ofthe above nature which contain only at'rfilatively smalltamount of inorganic salt.

5'Glaims. (0111 252 309) 1941, Serial, No.5 409,434,; now ;P.a.tcnt;..;\;No.

,386,2.47,dated -Octoberg V v h s-app c i n: au ust gzagtlais v realms xi eand a'dissolved inorganic saltfthen r-add tl r Water-miscible organic solvent toqithe aquasol in an amount sufficient to precipitate itheilinorganic salt and to permit, vsubstantially "thereafter removing the,v precipitated inorganic sa t, .wasflbyiiilfiltration, centrifuging or the jlike, and f nally .remoyingmthet water by distillation.

,"jllhej above.process-results in the production water i e, contain not more thanabout 1%-"of 'f'watenjf, lrodugts containin only traces 'of water will, 7 however, easily be"'obtained in accordance withjjth invention by subjectii the above sols waterni iin scibl The organic solvent initially employed should eflof such", a, nature a to cause substantially complete precipitation of inorganic salts and anhydrous organic solvents yghich are vofs-un-,.; should either have a boiling point higher-than usuallyhigh concentrations, e. g. contain as much gas twenty-five per .centoxide on more.

A further obiectoftheinvention is to prepare ,sols' .of, the type; described, containing either twaterrmisciblesor waterflmmiscible organic s01. -t:.'either by' itself or in combination with athird vents as-the continuous phase.

thatgcf water, i; e,'siifiiicientlyhigher to permit substantially, complete removal of the water by si n rzley'I..dlisti1lation,v ,or' it should be capable: "of mf orming a constant boiling mixture'with water,

or, afplura'lity, of additional components, which Jnixturecanjthen be" fractionallyl or otherwise distilled 'ofidleavingqas the residue a $01 containing llh' desired organic liquid as the dispersliablepsolventpfor forming abinaryC.*B.M. (constant; b'oilingsmixturey with water is normal prQDyLalcohol, whichrnot only is highly miscible with water, :butis relativelyfcheap and may be Still. further objects and advantages of the.in-,. -A0lreadily.obtainedlin large quantities. .Ethylalconvention will appear;;fromt.the .follovving description and appendedclaims. Y Beforeexplaining in detail the; present, invention, ,vhowevenliti is to be; understood that the-inventiomisnot limited the prior art.

Thelnventioni fizin een ma by "first l holmay also beused in accordance with this inventionrbutwas ethylalcohohdoes not form a satisfactory binary C(BIM. with water forjthe purposes of thisdnvention, a third component,

kinhits application to the details describedhereinflyidsuchlwas benzene, :d'ichloroethylene, trichloro- A since-the invention is v=capab1e of. other embodiyments andof-= beings-practiced. or ,carried;-,out in various :ways, Also-.it.-is-, to be understood that the phraseology or terminologypmployed herein is forlthe purpose of -rdescriptionand not of firmlethylalcoliol as. the continuous Phase. 1 tation. and it isnot intended to limitsthe invention claimed hel'einslaeyond1 the requirements l of ethylene, andgthefjlikarisn added, vvhichforms,v a smixturencapablefof boiling oil as; a1.ternary 0.? B; 1M. This, mixture is fractionally distilled i1 0 produce. asol-having substantially anhydrous .The sols lmade ,by distilling-constant, boiling mixtures, such as. those described, above, cannot only be made in an unusually high state of concentration, butare substantially free for water.

tiormi ngranra uasolscontainina. ancolloida-l ,inor: ikLThussthem-rnay be directlylmade ,withsa's little as 1 or less of H20. Moreover, they may be readily processed, as by replacement, to produce sols having relatively low boiling or high boiling water-miscible or immiscible organic solvents as the continuous phase. For example, the ethyl or propyl alcohol in the sols prepared as described above may be replaced with such organic liquids as Cellosolves, high boiling alcohols, ethers, ether-alcohols, ketones, esters, aliphatic and aromatic hydrocarbons and the like, by mixing the initial alcohol sol with one or more of the above solvents and distilling off the initial alcohol, either as such or in the form of a constant boiling mixture. The resulting sols have been found to contain even less water than the sols prepared directly from the constant boiling mixtures.

'As suitable organic solvents or liquids for replacing the initial alcohol sols may be mentioned such substances as Cellosolve, methyl and butyl Cellosolve, the butyl and amyl alcohols, diethyl Cellosolve, diethyl Carbitol, methyl isobutyl ketone, ethyl and. butyl acetate, benzene, toluene, and aliphatic hydrocarbons, such as lactol spirits.

Another method of further reducing the water content of sols formed from binary constant boiling mixture, such as the propyl alcohol sol prepared as described above, involves forming a ternary constant boiling mixture by adding to the resulting sol an organic solvent, such as benzene, dichloroethylene, and trichloroethylene and an additional quantity of the original organic solvent, and then fractionally distilling the resulting ternary mixture. The distillation product is an organosol containing only a trace of water. Thus, in the case of propyl alcohol it is possible to distill off both binary and ternary constant boiling mixtures with the result that sols having this alcohol as the continuous phase may be readily made containing very minute amounts of water.

The sols prepared from ternary constant bolling mixtures and containing only a trace of water, such as the propyl alcohol and like sols prepared as described immediately above, may be readily converted to sols containing water-immiscible organic solvents as the continuous phase. For example, the propyl alcohol in such sols may be replaced by toluene or other hydrocarbons by merely mixing the hydrocarbon with the substantially water free alcohol sol and distilling the resulting mixture. Sols of this nature are ordinarily very difficult to obtain, but may be readily prepared in accordance with the above method. The organic solvent or liquid employed should be added to the aquasol in suificient amounts not only to precipitate the inorganic salt contained therein, but to prevent gelation during the early stages of the distillation during which method may however be employed, depending upon the particular oxide sol which it is desired to prepare.

In general, it is preferable to use aquasols having a high concentration of the colloidal oxide" vent thanvlould otherwise be required to precipitate out the inorganic salt and also requires less distillation to remove water.

It is also usually preferable, particularly in the case of silica sols, to repare the aquasol and to precipitate the salt at temperatures of not above 15 C. Moreover, it is usually preferable to prepare and use an aquasol having a pH of between 2 and 4 to insure maximum stability during the preparation of the organosols. However, the invention should not be limited in these respects, as it is possible to obtain stable and substantially anhydrous sols of high concentration without resorting to temperatures below normal, and without operating in the above mentioned pH range. A more complete and thorough understanding of the invention will be obtained from the following examples:

Ezcample I.-Three hundred fifty-eight pounds of sodium silicate containing 28.7% SiO2, 8.9%

NazO and 62.4% H2O are diluted with one hundred sixty-two pounds of water. This mixture is then added to one hundred sixty-three and onehalf pounds of 31% sulfuric acid and the mass is agitated to distribute the silicate throughout the acid. The mixing is carried out in a suitable acid resistant apparatus at a temperature of about 15 C., and results in a silica sol having a pH of about 2.5. One thousand three hundred and seventyfive pounds of Cellosolve are then added to the sol gradually with stirring, while maintaining the temperature at about 15 C. This causes precipitation of the inorganic salt, which is then removed by filtering or centrifuging. To the clear sol one thousand five hundred and forty pounds of additional Cellosolve are added so that the SiOz content is reduced to about 3%. The sol is then distilled in a lead still equipped with a stirrer and a fractionating column, the distillation being discontinued when the sol in the still is substantially free of water and contains about 25% SiOz.

Example II .-Three hundred fifty-eight pounds of sodium silicate containing 28.7% SiOz, 8.9% NazO and 62.4% H2O are diluted with one hundred sixty-two pounds-of water. This mixture is then added to one hundred sixty-three and one-half pounds of 31% sulfuric acid and the mass is agitated to distribute the silicate throughout the acid. The mixing is carried out in a suitable acid resistant apparatus at a temperature of about 15 0., and results in a silica sol having a pH of about 2.5. One thousand three hundred and seventy-fivepounds of normal propyl alcohol are then added to the sol gradually with stirring while maintaining the temperature at about 15 C. This causes precipitation of substantially all of the inorganic salt,

'Which is then removedby filtering or centrifuging. To the clear $01 one thousand five hundred and forty pounds of additional normal propyl alcohol are added, which reduces the SiO2 content to about 3%. The sol is then distilled in a lead still equipped with a stirrer and a fractionating column. During the distillation the refluxing ratio is maintained in such a manner as to obtain 73% propanol in the first 50% of the distillate, about 92% propanol in the next 20% of the distillate, and about 99% propanol in the last 30%, which leaves as a residue a sol containing about 25% SiOz. 7

Example III.-Three hundred fifty-eight pounds of sodium silicate containing-28.7% SiOz,

1 8-19 1 Nate: and 62.4 %""I-I2O "are-' 'di1uted with one 1 organic tsolvents =used or present .in thei: finaizsol "hundred sixty' two pounds ot-Water. This mix- "may be leither water miscible:oriwatenimmisoible, tureisfthen added'to one hundred sixty-three high 'boilingor;low:boiling.: Moreover, they. may and-one l'i'alf pounds of 31% sulfuric acida'nd compriseor consist'of such hydrocarbons or;mix-

the mass'is--'agitated to distribute the-silicate 5 "turesof-mdrocarbons; as'. benzene,.toluene, lact ut-t e acid. 'The mixing is carried 'out tol .spir-its:.or1 thellikepwhicn heretoforeit shas *in a suitable-acid resistant' apparatus'at atem- 'vnot been. possiblato successfully prepare as sols peratureof -about" Cn 'and results in a silica f;th t e-.described. soil having a -I ofabout 2.5. -One=thousand Although the above examples refer solely, tmthe three hundred ahds'eventwfive P s thyl -lo -preparation2'of organosols containingv an individalco o Kco ta about 92% CzHsOH by ua'l .organicisolvent;it-shouldloeunderstood that ht) are then added to the Sol gradually with ctheinventionis notlimited tosuch sols, and that St While g' mperature at nsolsrmaylalsosbeiprepared;containing mixtures-10f :.about'15 CpiThisrcauses precipitation of sub- :-.organic;so1vents.- L'For example an'organosoln ay s a y all of the inorga io---- 1t, Whichais.Ie-n ebe iprepared.directlyrusing amiXtureof watermoved y filtering rwce t i e na. To e Clear miSCibIEQSQIVGHtSJ instead; of just one, ormthe 501 one thousand fivehuridredand forty po ---solventor solventsin theinitial organosol maybe of additional alcohol are -ladded, whichizreduoes :replacedvbyiany suitable mixtu e 'o o 'iL-t-he SiOaxcontent..to..ab.out13% i -.The 501i is'izthen went-, which; in uchtcase may ,be either waterildistilledwinn a..lead.. still equipped with a Fistirrerm t ihl ("and aufractionatingcolumn having 23 theoretical The term rganic solventghgmployed herein p Eight hundredla'nd ten pounds of benZOl and in the appended claims is intended to refer are gradually introduced into the top of the colt t type of solvents commonly mployed in t u during e first P of the The field of coating compositions, such as varnishes,

um s ope t t ap y a d the tempera- 25 lacquers, and the like, and commonly understood ture at the t p i maintained t y P by chemists as suitable for such purposes. The reflux control, u til all of the lower aqueous layer term is also intended to include, however, alcohols, has been separated and removed. A high reflux which are usually t employed as 1 nt in ratio is then maintained until all the benzolthe coating m alcohol fraction has been removed. Substan- The term c w represents th mono tially anhydrous alcohol is then removed at a ethyl ether of ethylene 1 1, while methyl, ap d rate until the sol in the still contains an ethyl, butyl and diethyl C'ellosolve represents the S102 content of about 25%. methyl, ethyl, butyl and diethyl ethers of ethylene Example IV.A mi t containing one P glycol respectively. The term lactol spirits repby We of the Propyl alcohol 501 prepared resents a product consisting of homogeneous in accordance with E p e II, two parts by closely fractionated portions of petroleum crude wei ht of anhydrou normal pr n n oil which are derived from petroleum by distillaenli one-quarter parts by Welght of P811201 5- tion and constitute a mixture of hydrocarbons tilled in a distillation apparatus equipped Wlth at having an evaporation rate imilar to or clos to stilier and a fractionating column having 23 40 that of toluene. The product hasaspecific gravtheorctical plates. Which results fi in the w ity of .7313 at 60 F. and the following A. s. T. M. moval of the water layer which forms and then distillation range; in the removal of the C. B. M. containing normal propanol and benzol. The distillation is continued until the final dehydrated sol, containing only a trace of water, has been concentrated to OF a 2 S 02 eontent- Initialboilingpoillt 200 Example V.Five parts by weight of toluene Distilled Per cent Distilled Temperature are added to one part by weight of the normal 9% propanol sol containing 25% SiO2 obtained in accordance with Example IV. The resulting mix- This application is a division of my (Io-pending ture is then distilled in a distillation apparatus application Se fi September provided with a stirrer and a fractionating 001- 1941, now ate t 2, anted Octo e umn until all the normal propyl alcohol is re- 9, 5, whi is a ntinu t p rt of app imoved as a C. B. M. and the resulting toluene sol cation Serial fi y 1939, and contains an S102 content of about 15%. granted June 1942, a Patent Emample VI.Two and one-half parts by What I claim weight of butyl acetate are added to one part by The method of Preparing a ta e a d sub- Weight of the normal propyl alcohol sol containstantially an ydr us r an s l p s d of a c ling 25% S102 obtained in c rd n ith loidal inorganic oxide and an organic solvent ample II. The mixture is then distilled in a (115- w i h comprises forming an aquasol containin tillation apparatus provided ith tirrer nd a a colloidal inorganic oxide and a dissolved inorfractionating column until all the normal propyl genie salt, adding P py alcohol i an a ou t alcohol is removed, whereupon the distillation is sufiicient to prec p tate t inorganic sa t and continued until the resulting butyl acetate sol to per t substantially Complete removal f t residue contains about 25% Si02. water in said aquasol by distillation, then remov- As indicated by the above examples, the method ing the pre p t inorganic Sa t, re ov g comof this invention not only permits the production p et y t e Water y distillation, a then adding of highly concentrated and stable organosols an or anic solv n elected f m he r p which are substantially free of water, but they 7 sisting of butyl alcohol and butyl acetate, and render it possible to prepare substantially salt em e p pyl alcohol by Simple distillationfree sols having a wide variety of organic solvents 2. The method of preparing a stable and subas the continuous phase, without resorting to stantially anhydrous organosol composed of colcumbersome and timeconsuming methods of reloidal silica and butyl acetate which comprises moving the salt, such as dialysis or the like. The forming an aquasol containing colloidal silica and a dissolved inorganic salt, adding normal propyl alcohol in an amount sufficient t precipitate the inorganic salt and to permit substantially complete removal of the water in said aquasol by distillation, removing the precipitated inorganic salt and removing completely the water by distillation, and then adding butyl acetate and removing the normal propyl alcohol by distillation.

3. The method of preparing a stable and substantially anhydrous organosol composed of colloidal silica and butyl alcohol which comprises forming an aquasol containing colloidal silica and dissolved inorganic salt, adding normal propyl alcohol in an amount sufficient to precipitate the inorganic salt and to permit substantially complete removal of the water in said aquasol by distillation, removing th precipitated inorganic salt and removing the Water by distillation, and then adding butyl alcohol and removing the normal propyl alcohol by distillation.

4. A stable and substantially anhydrous butyl acetate sol composed of a colloidal inorganic REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,386,247 Marshall Oct. 9, 1945 20 2,375,738 White May 8, 1945 2,391,253 Marshall Dec. 18, 194-5 

